Tooth pulp tester



Slept. 12, 1950 J. J. LOGAN ErAL TOOTHPULP TESTER Filed July 3, 1947 Patented Sept.v l2, 1950 l James J. Logan and `Robert BQ'Logan, I. Stratford, Pa.

Application` July 3, 1947, seriai 10,758,880

This* invention relates to tooth pulp testers and more particularly to electrical devices of this general character which are adaptedto deter`-` mine the condition of dental pulp bypassing electrical `current therethrough.` In the use of such a device, electric current is applied to a tooth to be tested by means of an electrode adapted to engage the tooth. Although the enamel and dentine of the tooth offer substantial resistance to the passage of current, a certain amount of current penetrates the tooth structure to `the pulp, which contains the nerve and blood vessels;v Usually a patient will experience a sensation when the current is passed throught a normal healthy tooth-pulp but will `experience no sensation if thepulp` isnon-vital. This has been relied upon in thepast as an indication of the condition of the pulp being tested. However, this is'not always a `true Vand accurate test as it has been foundthat in some cases a sensation may be felt even though the pulp is in poor condition. Sometimes a sensation is felt due to stimulation ofthe 'tissues surrounding the tooth rather than Prior tooth pulp testing devices generally have operated on the brute force principle. The object of such devices has been simply to force enough current through the toothpulp to cause the patient to feel a sharp sensation if the pulp is vital. The sensation produced by this method has been'in the nature of a-shock Whichis un-"I comfortable and sometimes painful to the patient? Moreover, such method involves the application ofwsubstantial voltageand is hazardous tothe patient. `Further still, such method cannot and does `not distinguish between a sensation' due to= irritation of the pulp and that due to stimulation of the tissues surrounding the tooth, and there fore it is unreliable.

The principal object ofthe preseni'finvention` is to-provide a tooth pulp `testing device Awhich operates,` on-adifferent principle than that of priori devices, andfwhichovercomes the objections- Thedevice of this inventionis of such devices. adaptedto apply a low D.`C. voltage to the tooth pulp sufficient only `to produce a milda'nd un' objectionable sensation, the voltage being-'of in# sufficient magnitude to constitute a hazardto the patient; Thedevice is 'furtheradaptedyto producea measurable current, in responseto the said voltage, in a circuit having no connection with the patient. The device is highlyfse'nsitiveand it isfable tordistinguish between the passage of current through the tooth pulp and the passage of current `throught-thev `tissues surrounding'- the 5 IClaims. (Cl. 12S-2.1)

tooth. .It therefore affords a reliable means for testing tooth pulp. I

Y-The invention may be fully understoodvfrom' thefollowing detailed description with reference tothe embodiment illustrated in the accompany-1 ing drawing, wherein Fig. 1 comprises a diagram'- matic illustration of the electrical circuit, and a` sectionalillustration of the electrodeprobe; and

Fig-2 is a fragmentary plan view taken along'I line 2-'2 of Fig. 1.

Referring to the drawing, there is provided af source of D. C. voltage which may comprise al transformer I and a rectifier 2 arranged in'wellknown-manner as illustrated. The output voltage of.` the `'conventional transformer and rectifier" combination shown, is'applied to a voltage dividerv 3' having adjustable contacts lland 5. "Afchokev coil 6 is`interposed between the voltagesourceandf the voltage divider 3, and an associatedrilter` condenser 1 is provided together with aswtchA 8 by which the condenser may be connected or disconnected as desired. The reason for this willy be explained later. i I

A D. C. 'voltage is derived from the divider `3 byfwayof adjustable contact 4 and is applied to'- a potentiometer 9. A D. C. voltage is alsode-` rived by `way of adjustable contact 5 and is apey plied to a second potentiometerl. Apositive voltage is derived from potentiometer 9 by wayfoff its adjustable contact II and is appliedto the anodes I2 andI3 of a double triode vacuumtube It.A It Will be noted that the adjustable-contact I I is connected directly to the anode I3 by Way of`1 conductor I5, while said contact is connectedto the anode I2 through an indicator I6 which may be a `conventional microammeter. A shunting resistor I'I and an associated switch IB are con# nected in shunt relation with the meter Mito4 enable variation of the deflection thereof.

Referring particularly to the double triode tube I4, the common .cathode heater I9 thereofmay-J be energized from a low voltage winding i2. of` the transformer I. It is important that the cathodes of the two tube sections be operated-- `at .the same temperature and this is achieved by Virtue ofthe common heater energized from asingle source. `Itewil be noted further that the grid 2l of the right-hand section of the'tube is connected to the cathode 22 through conductor' 23. It will be seen therefore, that the right-hand section of the tube has a certain established cur#- rent flow therethrough, depending uponthe volt-1V age applied to the anode I3. The 1eft-handsec tionof `the tube serves as an amplifier and; the right-hand section acts as a stabilizer, as here-f1 to the grauwe?offtneueit-naad section Kof 'the tube I4, through a patients body and through the tooth pulp, by means of an electrode 2l and Ytain value as determined by the position of sleeve -a probe device 28. The electrode 21 is adapted to be applied to some portion of the pat'ients body and this electrode is preferablyfinthe form of an arm band so that it is adapted to be apnv plied to an arm of the patient. `The probe de tact will affect the reading of the meter I6 and may give misleading information. To insure proper contact pressure between the probe electrode 3| and the tooth under test, the said elec` trode is carried by a slidable sleeve which is urged outwardly of the casing 29 by a spring 36. When the sleeve 35 moves relative to the casing, the shielded wire 3U also moves. Furthermore, the probe device 28 is constructed and arranged iso-effect an increase in the voltage derived from potentiometer Ill whenever the pressure of elec- `trole 3l on the tooth under test reaches a cer- "3'5. To 'this end, there is provided on the probe :device 28 an electrical switch comprising a pair fof adjacent contact fingers 3'! secured to casing vice 2a comprises a hollow oasingza through which a conductor 3i! extends. This conductor interconnects the grid 2t and a probe 3|, and it.; is provided with a grounded metallic shield 32 which is only partially shown. y The probe 3| isdapted fte -be-applied to. the surface of a tooth toi-beitested. Preferably the .30 is connected tota .metal tube ,Sla which' is ladapted to have thev probe` `3lA inserted therein. The probe mayv bev formed of wood; andit maybe dipped in a saline solution ,just before it is used. This makes 'it possible to discard the probe after a test and to use a new probe on the next patient. Moreoverwthe woodenprobe feels better to the patient thangdoes a metal probe.

fluring use of y the device, the low positive voltagefderived from potentiometer l is transmitted through thepatientsk body and the pulp thefrst circuit through the tooth pulp andploduces a `mild sensation .if the tooth pulp is vital.

A1 relatively .large current Flows in jthe second circuit,;and,the magnitude of this current is determined by the `voltage l on thegrid 26. The manner-in which a test -is `performed.will be clescribed later.

7A Vleak resistor 33, `connected between the ,gridv and cathode of `the left-hand section of tube rid,

serves to drain f'oi electrons `from Ithe grid. 2-6, after'athe yprobeSl has been removed trom the tooth. The electron. iiow through this` :resistor produces-aitemporary negative-bias on the .grid which checks electrons .emitted fromftliecathode 241and causes the plate current tov return tovzero.

It will lbe fnotedf that the right-hand vsection of `tubegl4 is connectedin shunt relation with the deft-'hand tube "section and 4the associated` meter i6. The right-hand tube section acts 'as a stabilizer for the left-handxtube section and insures that the :plate current of. thelatter `sectionwill yreturn to zero after each test. The right-hand tube section acts as a `continuous variable automatic fload across the vcommon D. fC. supply fonboth tube sections.

The making of proper contact of thefprobe electrode 3i with the tooth under test is Very important. The slightest variationof, the conf tactngers is connected in circuit with the winding 43 of a-relay 44 which may be supplied with energizing current from a low voltage source, e. g. 4the winding 20. The conductors 45 and 46 leading to the switch contact -iingers are'preferably provided with a grounded shield 4.7 which is only partially shown. The armature 48 of relay 44 controls a motor lil whoseshaft -is mechanically connected through reducing gears 50 and la `slip clutch '5i to the movable contact 25 of the potentiometer l0. The'broken line .representation indicates the mechanical connections of the said elements. The motor 49 may be energized Afrom any suitable source, e. g. the suppl-yllines leading to the 4primary ofstransiormer I.

IIn operation of the device, the .switch -8 will usually be closed to provide pure D. C. voltage. Oncethecontacts 4, Sand l l :have been adjusted to give the desired voltages, they need .not be moved and are not manipulated during Ya test.

i Prior to the `making of a test, the 4Contact 25 is manuallyed-justed -to the zero voltage position, i.-e. to the ground-end of-potentiometer -.|0. This is venabled by theslip clutch 5l. The lmeter I.6 reads zero.

- With lthe e1ectrode=21 andthe probe 3l applied tothe ypatient Aas above described, the operator exerts sucient pressure on the tooth under Atest to cause closure of the :switch on device 2,8, thereby causing operation of themotor'49. The motor drives contact 25 slowly, through reduction gears 50, in a direction `to apply an increasing lvoltage to the electrode 21. When the'patient experiences a mild sensation, the-operator reads the meter I6 and immediately removesthe probe 3l. Theoperator then records the voltage and current -readings which serve to indicate the condition ofthe tooth pulp at that ltime. Since the voltage yreading -is important, the potentiometer 4I) should rbe provided with an indicating dial. The -recorded `readings .may be -compared with 'the results -of .earlier or later 'tests to-determine whether the condition of the 4tooth pulp has become better or worse. The -device enables making of successive tests under .identical conditions.

If fthe sensation felt by thev patient should'be due to the passage of current through'the tissue surrounding the tooth, rather l'than vto thevpassage-of current through the tooth pulp, :the-needle of. meter I6 Willuctuateidue to the :fact .that

yment over prior devices.

tissue resistance varies slightly and the device is sufliciently sensitive to detect the voltage variations caused thereby. The fluctuation of the meter needle indicates at once to the operator that he is not getting a proper reading with respect to the tooth pulp.

Whenever the application of pure D. C. voltage fails to produce a sensation, the switch 8 may be opened to disconnect the filter `condenser l and thus produce a ripple of the D. C.' voltage. This will sometimes cause the tooth pulp to respond when it will not respond to pure D. C. voltage.

A device constructed according to the present invention has been used by an experienced dentist and has been found to be a great improve- The aforementioned advantages have actually been demonstrated.

While a particular embodiment of the invention has been illustrated and described, it will be apparent that the invention is not limited thereto. If desired, a recording microammeter may be employed to make a record on a card. In this way, successive records could be made on a single card of the condition of the pulp of a tooth at different times.

We claim:

1. In aA tooth pulp tester, a double-triode vacuum tube, means for applying a positive potential to the anodes of said tube, current indicating means included in the anode circuit of one triode section of said tube, means connecting the other section of said tube in parallel relation with the first section and said indicating means, and means for applying a relatively low positive potential to the grid of the iirst section through the tooth pulp to be tested.

2. In a tooth pulp tester, a double-triode vacuum tubell vmeans for applying a positive potential to the anodes of said tube, current indicating means included in the anode circuit of one triode section of said tube, means connecting the other section of said tube in parallel relation with the rst section and said indicating means, a probe adapted to be applied to a patients tooth to be tested, means connecting said probev to the grid of the rst tube section, an electrode adapted to be applied to some part of the patients body. and means for applying a relatively low positive potential to said electrode.

3. In a tooth pulp tester, a double-triode vacuum tube, means for applying a positive potential to the anodes of said tube, currentv indicating means included in the anode circuit of one triode section of said tube, means connecting the other section of said tube in parallel relation with the rst section and said indicating means, a probe device including a probe adapted 6 to be applied to a patients tooth to be tested, means connecting said probe to the grid of the rst tube section, an electrode adapted to be applied to some part of the patients body, means for` applying a relatively low positive potential to said electrode, and means controllable from said probe device for varying said last-mentioned potential.

4.' In a tooth pulp tester, a double-triode vacuum tube, means for applying a positive potential to the anodes of said tube, current indicating means included in the anode circuit of one triode section of said tube, means connecting the other section of said tube in parallel relation with the first section and said indicating means, a probe device including a movable probe adapted to be applied to a patients tooth to be tested, means connecting said probe to the grid of the first tube section, an electrode adapted to be applied to some part of the patients body, means for applying a relatively low positive potential to said electrode, switch means on said probe device operable by said movable probe according to the pressure applied to the tooth under test, and means controlled by said switch means for varying said last-mentioned potential.

5. In a tooth pulp tester, a double-triode vacuum tube, means for applying a positive potential to the anodes of said tube, current indicating means included in the anode circuit of one triode section of said tube, means connecting the other section of said tube in parallel relation with the iirst section and said indicating means, a probe device including a movable probe adapted to be applied to a patients tooth to be tested, means connecting said probe to the grid of the rst tube section, an electrode adapted to be applied to some part of the patients body, means including a, potentiometer for applying a relatively low positive potential to said electrode, means including a motor for actuating said potentiometer, and switch means on said probe device operable by said movable probe according to the pressure applied to the tooth under test and adapted to control said motor.

JAMES J. LOGAN. ROBERT B. LOGAN.

REFERENCES CITED The following references are of record in the fue of this patent:

UNITED STATES PATENTS 

